Pen



FIG. 1 is a perspective view of the new design for a pen;

FIG. 2 is a side view in elevation of the new design;

FIG. 3 is a side view in elevation of the new design oriented at a position 90° from the view depicted in FIG. 2;

FIG. 4 is a side view in elevation of the new design oriented at a position 90° from the view depicted in FIG. 3;

FIG. 5 a side view in elevation of the new design oriented at a position 90° from the view depicted in FIG. 4;

FIG. 6 is a top view of the pen; and,

FIG. 7 is a bottom view of the pen. 

CLAIM The ornamental design for a pen, as shown and described. 